Modernism, postmodernism, and postmodernity are ways of shaping historical time into epochs
I’ve been working on a post tentatively entitled: “‘Modern movement’ in architecture gave rise to ‘an intellectual time bomb with a very long fuse’ (Ken Greenberg).”
The reference to an intellectual time bomb is from a previous post entitled:
Greenberg notes that in the aftermath of the European Industrial Revolution, which gave rise to deplorable living conditions in industrial cities, a “modern movement” in architecture emerged.
He characterizes the movement (p. 22) as “an intellectual time bomb with a very long fuse” fueled by good intentions.
The modern movement in architecture was motivated by what Greenberg calls (p. 22) “a sincere humanist urge” to address the substandard housing, overcrowding, pollution, noise, soot, disease, and other features of industrial cities that emerged after the Industrial Revolution.
At the upcoming post about the “modern movement” I will address such topics at greater length, with a focus on the role that Le Corbusier played, in construction of the “intellectual time bomb,” to which Ken Greenberg refers.
Modernism, postmodernism, and postmodernity
Reference to modernity (as in reference to the “modern movement” in architecture) brings to mind the related concepts of postmodernism and postmodernity, which are discussed at a previous post entitled:
A book I’ve been reading recently, entitled: The Transformation of the World: A Global History of the Nineteenth Century (2014), offers an overview, concerning the construction of historical epochs, that I find useful.
A passage (p. 48, in Chapter Two – “Time: When Was the Nineteenth Century?”), regarding such construction, reads:
One of several ways of shaping historical time is to condense it into epochs. To the modern European mind, at least, the past appears as a succession of blocks of time. But the terms used to describe epochs are seldom crystallizations of raw memory; they are the result of historical reflection and construction. Not infrequently it is a major historical work that first calls an epoch into being: whether it be “Hellenism” (Droysen), the “Renaissance” (Michelet, Burckhardt), the “late Middle Ages” (Huizinga) or “late antiquity” (Peter Brown). In many cases, academic neologisms have scarcely trickled through to a wider public: “early modern age” is a good example. This was first proposed as the name for an epoch in the early 1950s. The term soon won recognition in the historians’ lexicon, being seen almost as the fourth epoch of world history on a par with the previous three – and thus fulfilling the apocalyptic fourfold vision of world empires in the Old Testament.  Confusion reigns when it comes to “modernity,” a concept applied indiscriminately and with a host of arguments to every century in Europe since the sixteenth, and even to “medieval” China in the eleventh: social history has employed it for the period since the 1830s; cultural-aesthetic theory limits it to one not earlier than Baudelaire, Debussy, and Cezanne.  The ubiquitous talk of modernity, postmodernity, and “multiple modernities,” nearly always without even an approximate chronological definition, naturally indicates that the sense of epochs has been steadily weakening. It may be that “early modern age” is the last construction of its kind that commands general acceptance within university faculties. 
Such an overview offers a useful sense of what these terms mean.